1. Field of the Invention
This invention relates to a furnace temperature control apparatus using adjustment input. In particular, the invention relates to an apparatus for temperature control of a furnace running in repetition of a certain operating pattern of temperature change with time, which apparatus suppresses furnace temperature change due to regularly occurring operating pattern.
2. Description of the Prior Art
A typical furnace system will be briefly reviewed by referring to FIG. 9. A furnace 1 has a body 1a carrying a plurality (e.g., p pieces) of heaters 2. A plurality (e.g., s pieces, s&gt;p) of temperature sensors 3 are disposed in and around the furnace 1 at positions suitable for measuring the state (x) such as temperature of the furnace 1. It is assumed here that the control variables are a set of inside temperatures (y) at m points (m&lt;s) in the furnace 1. The control variables in this case are a part of the state (x).
FIG. 24 shows a block diagram of a conventional controller 12 for controlling the temperature of the furnace 1. The state (x) and the inside temperatures (y) are fed back to the controller 12, and the controller 12 generates p pieces of manipulating variables (u), representing magnitudes of quantities (to be manipulated), so as to minimize errors (e) of the inside temperatures (y) from corresponding preset values (r) therefor. The manipulating variables (u) are applied to the heaters 2 of the furnace 1.
To control digitally the furnace 1, the state (x) of the furnace 1 is given by the following discrete state equation, and the furnace temperature control is generally treated as a servo problem using the multi-variable control theory. EQU x(k+1)=Ax(k)+Bu(k) EQU y(k)=Cx(k)
here,
x(k): state vector at time k, being a real vector of s dimension. PA1 u(k): manipulating variable vector at time k, being a real vector of p dimension PA1 y(k): control variable vector at time k, being a real vector of m dimension PA1 A: an s-row s-column matrix of real coefficients PA1 B: an s-row p-column matrix of real coefficients PA1 C: an m-row s-column matrix of real coefficients
With the controller 12 of FIG. 24, it is possible to deal effectively with various changes, such as step-like changes in target values and disturbances. In practice, the furnace 1 is often run in repetition of a certain operating pattern of temperature change with time, such as the curve T of FIG. 11C, which pattern is given in the form of a series of preset temperature values (r). With the conventional controller 12, each cycle of the repetition is carried out in the above-mentioned manner so as to run as closely to the certain operating pattern as possible.
However, it is not possible with the conventional controller 12 to improve the tracking performance with respect to the certain operating pattern T even after repeated runs of such pattern T. The tracking performance refers to the closeness of the actual inside temperatures (y) of the furnace 1 to the preset temperature values (r) representing the operating pattern T. Further, actual run of the furnace 1 often encounters repetitive disturbances occurring at certain timing in each cycle of the operating pattern T, such as loading and unloading of works. The conventional controller 12 cannot reduce the effects of such repetitive disturbances even after repeated runs thereof.